• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.63-68
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• 2008

We investigated the recycling method to re-plasticize cross-linked polyethylene by using supercritical methanol. The cross-linked polyethylene is successfully fragmented to thermoplasticized polyethylene with little degradation reactions in supercritical fluids. The thermo-plasticization reaction was accelerated with increase in temperature in the range from $360^{\circ}C$ to $400^{\circ}C$, resulting in decrease in crosslinking density, molecular weight and mechanical properties. However, the thermoplasticized polyethylene at $360^{\circ}C$ showed comparable tensile strength and impact strength with a raw resin of crosslinked polyethylene. Chemical structure of main chain of polyethylene was not affected by reaction condition.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.257-263
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• 2012

Biodiesel is a renewable energy which is nontoxic and acting as a replacement for conventional diesel which derived from fossil fuel. Classified biodiesel producing way such as acid, base, supercritical and enzyme methods, this study focused on eco-friendly production of biodiesel using supercritical and immobilized enzyme process. Assuming a plant with a production rate of 10,000 tons a year, a PRO II simulator program was used to simulate the product conversion rate and total energy consumption. The product conversion in supercritical process and immobilized enzyme was found to be 91.17% (including 0.9% glycerol) and 93.18% (including 1.0% glycerol) respectively. The result shows that the efficiency of immobilized enzyme process is higher compared to supercritical process but having lower end product purity. From the energy consumption point of view, supercritical process consume about 8.9 MW while immobilized enzyme process consume much lower energy which is 3.9 MW. Consequently, this study certifies that energy consumption of supercritical process is 2.3 times higher than immobilized enzyme process.

• KSBB Journal
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• v.19 no.4
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• pp.284-287
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• 2004

The purpose of this study was to find an optimum extraction condition of acanthoside-D from acanthopanax cortex with supercritical carbon dioxide as a solvent. In this effort, effects of the extraction conditions including pressure, temperature and presence or absence of a cosolvent on the extraction efficiency were investigated. The ethanol, water or 50% methanol was used as a cosolvent whilst the operating pressure ranged from 200 bar to 300 bar. The acanthoside-D concentrations were determined by means of HPLC equipped with a UV detector. From the results, it was observed that increase of higher pressure led to the higher extraction efficiency. Further, water was found to be the best cosolvent among the entrainers tested.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.5
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• pp.99-106
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• 2008

Metal ions such as Cu and Cr were extracted from the Cu, Cr and Ag impregnated active carbon by contacting the solid surfaces with supercritical carbon dioxide(Sc-$CO_2$) containing chelating agents. About 10g of the active carbon sample were loaded in a vertical tube extractor contacting with $CO_2$ flowing from the bottom of the tube for 6hrs. The ligands used were acetyl acetone(AA) and Cyanex-302(C-302). Water and methanol were used as entrainers to study the effect of co-solvent to $CO_2$. Experimental results showed that C-302 was more effective than AA in removing Cu with the maximum extraction of 42.0wt%, while 57.6wt% of Cr was extracted with AA from the sample.

• KSBB Journal
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• v.26 no.5
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• pp.453-458
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• 2011

In this study, two different extraction techniques, organic solvent extraction and supercritical carbon dioxide ($SCCO_2$) extraction, were employed to evaluate the extraction efficiency of oil from Chlorella vulgaris. In the organic solvent extraction, the effects of various organic solvent on the extraction yield were investigated. The $SCCO_2$ extraction was carried out while varying such operating parameters as temperature, pressure, $SCCO_2$ flow rate, and cosolvent. About 4.9 wt% of oil was extracted from ground Chrollera vulgaris for 18 h when dichloromethane/methanol (2：1, v/v) was used as an extraction solvent. The oil yield of the $SCCO_2$ extraction was found to be very low (0.53 wt%) and to increase up to about 0.86 wt% with the addition of cosolvent.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.220-224
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• 2017

In this study, we investigated a new recycling method of phenol resin, which is widely used to make electric insulation boards and adhesives, into carbon particles by using supercritical fluids. Because phenol resin is insoluble and infusible, most of the phenol resin wastes are buried in the ground or incinerated, which leads to environmental pollution. Therefore, development of a new method to recycle phenol resin waste is an urgent issue. In this study, phenol resin waste was treated with four sub/supercritical solvents: ethanol, acetone, water, and methanol. For all the sub/supercritical solvents, the phenol resin wastes were broken down into carbon nano particles at much lower temperatures than that required in the existing carbon particle manufacturing processes. We investigated the difference of morphologies and physical properties of recycled carbon particles according to the use of various solvents. As a result, carbon nano particles with the same amorphous structure were obtained from phenol resin waste with the usage of various sub/supercritical solvents at much lower temperature.

• Clean Technology
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• v.11 no.3
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• pp.141-146
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• 2005

The composite membranes were made by grafting using supercritical carbon dioxide (scCO2) impregnation and polymerization procedures. The membranes were synthesized by changing amount of monomer. The polypropylene grafted polystyrene sulfonic acid (PP-g-pssa) membranes were characterized with various methods. The morphology and structure of PP-g-pssa membranes were analyzed with scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). As amount of monomer was increased, ion conductivity, cell performance was increased and methanol permeability was decreased. However PP-g-pssa membranes with 1.5g monomer and over had similar values of methanol permeability, ion conductivity and cell performance.

• KSBB Journal
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• v.11 no.1
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• pp.100-106
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• 1996

The extraction of taxol and baccatin III from the ground needles of Taxus cuspidata were carried out by using supercritical carbon dioxide with and without cosolvents such as ethylacetate and methanol at 300 bar and 313K. Taxol is a promising anticancer agent and baccatin III is a precursor of semisysthesis of taxol. The taxol and baccatin III contents in the extracts were determined by a HPLC. The highest yields of taxol and baccatin III could be obtained by the supercritical extraction with 3wt% methanol and ethylacetate, respectively, as cosolvents. It was also found that the selectivity of taxol and baccatin III were 0.117 and 1.245wt%, respectively, with 0.7wt% ethylacetate, which demonstrated that the selectivity of taxol and baccatin III were increased about 1.8 and 19 times than those of conventional organic solvent extraction.

• Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.123-130
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• 2015

Seaweed Sargassum horneri extracts were obtained using supercritical carbon dioxide ($SC-CO_2$) and different solvents. $SC-CO_2$ was kept at a temperature of $45^{\circ}C$ and pressure of 250 bar. The flow rate of $CO_2$ (27 g/min) was constant during the entire 2-h extraction period, and ethanol was used as a cosolvent. Six different solvents [acetone, hexane, methanol, ethanol, acetone mix methanol (7:3), and hexane mix ethanol (9:1)] were used for extraction and agitated by magnetic stirring (250 rpm) in the dark at $25^{\circ}C$ for 20 h; the ratio of material to solvent was 1:10 (w/v). Antioxidant properties of S. horneri extracted using $SC-CO_2$ with ethanol and different solvents have shown good activity. The highest activity belongs to $SC-CO_2$ with ethanol extracted oil, showing DPPH, ABTS, total phenolic content, and total flavonoid levels of $68.38{\pm}1.21%$, $83.51{\pm}1.25%$, $0.64{\pm}0.02mg/g$, and $5.57{\pm}0.05mg/g$, respectively. The S. horneri extracts showed a significant correlation between the antioxidant activity and phenolic content. Based on these results, the $SC-CO_2$ extract (ethanol) of the seaweed extract from brown seaweed may be a valuable antioxidant source.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.88-92
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• 2012

Decrosslinking of crosslinked polypropylene(XLPP) in supercritical methanol was investigated compared with that of crosslinked polyethylene(XLPE). Effect of reaction temperature and initial gel contents was studied using a batch reactor. Gel contents of samples before and after reaction were measured for quantitative analysis. As reaction temperature and initial gel contents increased, the decrosslinking rate increased. The rate of decrosslinking reaction is dependent linearly on the gel contents. Experimental results indicated that the decrosslinking of XLPP was faster than that of XLPE, and it was confirmed quantitatively by the calculation of kinetic constants. In conclusion, it is considered that XLPP has better recyclability than XLPE.